Copper-silicon-zinc-tin-lead alloy



Patented Mar. 30, 1937 Uni-Tao STATES PATENT OFFICE Conn, by Sarah H.Bassett,

Cheshire, Conn.,

, executrix; said Bassett assignor to The American Brass Company,Waterbury, Oo'nn., a corporation of Connecticut No Drawing. Originalapplication November 25,

Q 1 1933, Serial No. 699,710.

Divided and this application December 15, 1936, Serial No.

3 Claims. (Cl. 75-158) This invention relates to copper base alloyscontaining silicon, zinc and tin, and has for its chief object toimprove certain characteristics of such alloys, and particularly theirmachinability or free cutting properties. The free cutting properties ofthese copper base alloys are sesecured with little or no depreciation oftheir physical properties by the addition of lead in relatively smallamounts.

This application is a division of the prior application of William H.Bassett for Copper silicon alloys filed November 25, 1933, Serial No.699,710.

A number of copper base alloys containing silicon have gone into quiteextensive use, it being found that the addition of silicon up to certainamounts to copper produced alloys which were highly resistant to thechemical action of certain acids and other corrosive liquids. It was,however, found'that the addition of silicon rendered the alloy hard andvery brittle and difiicult or practically impossible to work, and otherelements such as zinc and tin wereaddedto overcome these difiicultiesand improve other properties of the alloy such as strength, toughness,etc., and still retain the resistance to corrosion. It was found thatfor practical purposes the range of silicon was up to approximately6.5%, and my invention therefore relates to copper base alloys,containing from approximately 0.1% to approximately 6.5%.silicon, 1% to12% zinc, and 0.5% to 6% tin.

It has been known to improve the machining qualities of copper or brassby the addition of lead, but it has been generally considered and alsothe literature would indicfite that in alloys containing silicon leadwould be thrown out of the mixture by the silicon. This was alsoindidated where there has been a mixture of leaded scrap with coppersilicon alloys. In other Words it was generally supposed that withsilicon present the lead would settle to the bottom of the crucible orfurnace due to its high density. He has found, however, that with smallamounts of lead in copper base alloys containing silicon, zinc and tinin the amounts above noted the lead is dispersed as fine particlesthroughout the mass, greatly improving its machinability or free cuttingqualities. He has found that this effect is secured with amounts of leadfrom approximately 0.1% to approximately 1.5%, the preferred range beingfrom approximately 0.25% to approximately 0.4%, as above about 0.4 or0.45% lead it is difiicult or practically impossible to work the 55alloy in mill practice.

Zinc was added to the copper silicon alloy to produce alloys which couldbe worked either hot or cold and therefore were less brittle while stillremaining highly resistant to the corrosive action of certain acids andother corrosive liquids. It also rendered the alloys harder, tougher,

stronger and more elastic than the common brasses. 'I'hese alloys Withthe lower zinc contents are hard, malleable, ductile and tough.Increasing the zinc gives alloys which are stronger, harder, moreelastic but less malleable. The addition of zinc also gives soundercastings as the metal has less tendency to absorb furnace gases thancopper-silicon alloys containing no zinc and the resistance to thecorrosive action of certain liquids is also improved. The hardness ascast increases with additions of zinc up to about 15 percent.

The addition of tin to the alloy increases the corrosion resistance tocertain liquids and also adds strength.

The addition of zinc.used is from approximately 1 to 12% and theaddition of tin is from approximately 0.5 to 6%. There may also beadditions of manganese from approximately 0.01 percent to 3 percent tothese alloys.

The addition of these elements to copper base alloys composed mainly ofcopper and silicon produce sound strong alloys which are highlyresistant to the chemical action of certain acids and corrosive liquids.

Difiiculty, however, was experienced in machining these alloys as amongother things the chips were tough and came off in long continuousspirals tending to clog the tools, and the tools would not stand up andcutting speed was rela-- tively low. It was found however that by theaddition of the above named quantities of lead to these alloys they wererendered much more free cutting, and the chips instead of coming oii inlong continuous spirals broke up into short lengths easily clearing thetool, and in short converted the alloys into free cutting alloys withlittle or no depreciation of their physical properties, such asstrength, toughness, workability, and resistance to corrosion.

Having thus set forth the nature of his invention, what he claims is:

1. A copper base alloy which is characterized by free cutting propertiesand resistance to corrosion comprising approximately 0.1% to 6.5%silicon, 1% to'12% zinc, 0.5% to 6% tin, 0.1% to,0.45% lead, and balancecopper.

2. A copper base alloy which is workable and characterized by freecutting properties and resistance to corrosion comprising approximately0.1% to 6.5% silicon, 1% to 12% zinc, 0.5% to 6% tin, 0.25% to 0.4%lead, and balance copper.

3. A wrought metal article-composed of a cop- 5 per base alloycharacterized by free cutting properties and resistance to corrosioncomprising approximately 0.1% to 6.5% silicon, 1% to 12% zinc,

0.5% to 6% tin, 0.1% to 0.4% lead, and balance copper.

' SARAH H. BASSETT,

Emecutria: of the Last Will and Testament of 5 William H. Bqssett,Deceased.

